Abstract
The influence of diluting silane (SiH4) with hydrogen (H2) on the structural and electrical properties of highly boron-doped microcrystalline silicon prepared by plasma enhanced chemical vapor deposition (PECVD) was investigated. The structure of the film has been observed to change from the amorphous to the microcrystalline dominant phase, with increase of the hydrogen dilution. The silicon-hydrogen bond evolution was analyzed using Raman spectroscopy. The silicon-hydrogen vibrational mode in the range 1900-2200 cm-1 was deconvoluted into two stretching vibration modes at 2000 and 2100 cm-1. For low hydrogen dilution, ascribed to the amorphous dominant phase, the Si-H stretching mode at 2000 cm-1 has been found to dominate, while for high hydrogen dilution, assigned to microcrystalline phase the Si-H stretching mode at 2100 cm-1 raised and becomes comparable with the one at 2000 cm-1. This result indicated that in our film deposited with lower hydrogen dilution hydrogen atoms is bounded in isolated silicon, while in higher hydrogen dilution a large fraction of hydrogen atoms accommodated in cluster. The transport properties of the films are also investigated.